1. Field of the Invention
The present invention relates to a camera device covering a camera with a housing, and particularly relates to a camera device able to prevent dew condensation.
2. Background
In the conventional camera device such as a monitor camera for the outdoors, etc., the dew condensation is generated by the difference between the temperature of an external environment and a camera interior temperature. The temperature of the camera interior is influenced by generated heat of an electronic circuit of the camera, etc. It is required that such dew condensation is prevented. The field of view can be preferably held by the prevention of the dew condensation.
In the conventional camera device, a blower and a heater are arranged within the housing, and a warm wind is sent to a shooting window portion to prevent the dew condensation. In another conventional technique, it is proposed that an optical glass and a filter of a double structure are arranged in the shooting window portion, and nitrogen gas is sealed between a clearance between the optical glass and the filter, or the clearance between both the optical glass and the filter is set to a vacuum. Such a technique is disclosed in JP-A-10-285454 (third page and FIG. 4).
However, in the conventional camera device, dew condensation preventing ability is low since only the blower and the heater are used. It is necessary to arrange comparatively large-sized blower and heater so as to obtain a sufficient dew condensation preventing effect. Further, when the nitrogen gas is sealed in the clearance between the optical glass and the filter or the clearance is set to a vacuum, it is not easy to hold the clearance portion in a seal state. Therefore, it is not easy to obtain high dew condensation preventing ability.